Patient-specific craniofacial implants

ABSTRACT

Disclosed herein are patient-specific craniofacial implants structured for filling bone voids in the cranium as well as for simultaneously providing soft tissue reconstruction and/or augmentation for improved aesthetic symmetry and appearance. Pterional voids or defects generally result from a chromic skull deformity along with a compromised temporalis muscle or soft tissue distortion from previous surgery. When muscle atrophy occurs in the pterion, temporal hollowing generally results where there would be soft tissue but for the atrophy. The patient-specific temporal implants herein are configured to have an augmented region adjacent the temporal region of the cranium in order to account for and correct any such temporal hollowing.

FIELD OF THE INVENTION

The present invention relates to patient-specific craniofacial implantsand methods of designing such implants for filling both bone and softtissue in the temporal region of a patient's head.

BACKGROUND OF THE INVENTION

Certain congenital conditions and acquired deformities related tosurgery, irradiation, and/or trauma may result in varying sized andshaped voids in bone and soft tissue. For example, severe impacts to thehead could leave the frontal, parietal and/or temporal areas of thecraniofacial skeleton in need of repair. Cranial bone voids are commonlyfilled throughout the anterior, middle, and posterior cranial vaults,for example, using autologous bone flaps, standard or customizedalloplastic implants, titanium mesh, biologic absorbable materials,tissue engineered substrates and/or liquid methyl methacrylate in orderto provide much needed cerebral protection. However, in times wheresecondary cranioplasty requires a bone substitute, temporal hollowingneeds to be corrected and/or prevented.

While cranial bone voids present via congenital deformities or traumaticinjuries may be filled using any one or more of the above means toachieve structural soundness, replacement of soft tissue structures thatoverlie the bone void being filled and underlie adjacent skin tissuegenerally has to be accounted for in order to achieve a preferablecosmetic result. Bone flaps, standard or customized alloplasticimplants, titanium mesh, and liquid methyl methacrylate that are used tofill bone voids do not account for soft tissue atrophy in the temporalarea of the skull. Thus, these bone void filling means do not provide anadequate aesthetic reconstruction of this area.

In many cases where bone is filled in the temporal region, the softtissue loss in this area generally results in concavity referred to astemporal hollowing. This reflects a deficiency in the bulk of thetemporalis muscle or overlying temporal fat pad. Many patients who haveundergone neurosurgical procedures that damage the integrity of thetemporalis muscle during temporal or pterional craniotomy surgery in thetemporal area are left with this concavity. Both aesthetic andreconstructive procedures that violate the temporal fat pad may resultin temporal hollowing. As such, the area of concern is a directdeformity related to a few etiologies such as temporalis muscledisplacement or foreshortening from previous surgery, temporal fat padatrophy, or soft tissue contraction from irradiation or aging.

In patients with the common temporal hollowing, the top or cephalad partof the deformity is generally a concave depression due to the missing,above-mentioned etiologies. In addition, directly underneath andneighboring this concave depression is a convex bulge (directly cephaladto the zygomatic arch) that often originates from a displaced temporalismuscle. In some common instances, the temporalis muscle cannot bere-inserted since the bone flap is unable to be placed back intoposition, thereby leaving an absent fixation point adjacent the temporalcrest. This not only accentuates the neighboring concave deformityabove, it sometimes causes dynamic distortion during chewing since thetemporalis muscle is involved with mastication.

Other reasons for the cephalad deficiency, or other head deformities,may entail temporal fat pad wasting, which is a defined layer ofanatomical fat between the skin and the skull which adds to the normalbulk of one's temporal region. It is often a sign of youthfulness. Manypatients who have undergone neurosurgical and/or temporal procedures maylose the integrity of the temporalis muscle during temporal or pterionalcraniotomy surgery. Both aesthetic and reconstructive procedures thatviolate the temporal fat pad, such as coronal incisional approaches, forinstance, may also result in temporal hollowing, which can happen if asurgeon devascularizes the area with dissection or if the area hasreceived irradiation or tissue resection for oncological treatment.

Numerous techniques have been described to augment the temporal area,including the placement of various standard or customized alloplasticimplants, titanium mesh, free fat grafts, dermal grafts, tissueengineered substrates, the injection and onlay of various absorbable andpermanent materials, loco-regional flaps, and, in some instances, freetissue transfer with microscopic technique. Temporal augmentation canrestore the preoperative appearance of these patients; however, suchaugmentation is generally performed in a subsequent procedure after aninitial procedure of filling a bone void in this area. Thus, thesesolutions are problematic because a revision surgery is generallyrequired to correct the deformity, and the patient will likely exhibitaesthetic asymmetry prior to the revision surgery. There thus exists aneed for a patient-specific cranial implant that provides both bonyreconstruction and soft tissue reconstruction such that one or morerevision surgeries will generally not be necessary.

BRIEF SUMMARY OF THE INVENTION

As used herein, when referring to bones or other parts of the body, theterm “superior” or “cephalad” means upper or top, and the term“inferior” or “caudal” means lower or bottom. The term “posterior” meanstowards the back of the body, and the term “anterior” means towards thefront part of the body or the face. The term “medial” means toward themidline or center of the body, and the term “lateral” means away fromthe midline or outside of the body.

The patient-specific, dual-purpose temporal implants of the presentinvention are designed to fill a void in the skull while alsosimultaneously augmenting the pterional/temporal area. Preferably,alloplastic material is used in the construction of suchpatient-specific temporal implants. The mechanical properties of thealloplastic material used to construct these implants will allow them tocover the void and to recreate the soft tissue bulk that is preferablypresent in the temporal area prior to any injury and/or atrophyoccurring in a patient. The patient-specific implants of the presentinvention are designed to fill a cranial void while also restoringaesthetic symmetry by augmenting the temporal area of the skull tocounter temporal hollowing. Therefore, the patient-specific cranialimplants of the present invention may be used to replace a bony voidleft by a craniotomy either as a preemptive or prophylactic solution toaddressing aesthetic asymmetry that may occur due to atrophy of temporalmuscle or overlying fat pad of the bony void.

A first aspect of the present invention is a method of designing apatient-specific craniofacial implant for filling a void in a patient'sskull and for simultaneously replacing soft tissue comprises firstcreating a three dimensional model of the skull having the void, thencreating a preliminary implant model configured to replace the void inthe skull, and then creating an updated implant model by augmenting anouter contour of the preliminary implant model to account for softtissue loss or displacement in a temporal area such as the pterionalregion of the skull overlying at least a portion of the bony void.

In one embodiment of this first aspect, tomographic images of the skullof the patient are taken in order to create the three dimensional modelof the skull including the void. The preliminary model is created bymirroring contralateral bone of the void about a sagittal plane of thepatient. If the defect is bilateral, normal variations of soft tissue tohard tissue variance may be assessed by industry standards and utilizedfor unilateral or bilateral temporal implant fabrication. Suchassessments may be made as gender-specific for males and females sincethey are known to have different gender-specific anthropometrics.

In another embodiment of this first aspect, creating a three dimensionalof the skull having the void may include taking two-dimensional orthree-dimensional photographs from various views for confirmation ofaesthetic deformity size and/or shape of the void.

In another embodiment of this first aspect, augmenting the outer contourof the preliminary implant model comprises providing a firstcross-sectional view of the preliminary implant model in a coronalplane, providing on the first cross-sectional view a vertical linetangent to a most lateral portion of a zygomatic arch of the skull ofthe patient, and providing on the first cross-sectional view a contourline from a temporal crest of the skull until the contour lineintersects the vertical line tangent to the most lateral portion of thezygomatic arch in the first cross-sectional view, the contour linerepresenting a first portion of the augmented outer contour of thepreliminary implant model.

In yet another embodiment of this first aspect, augmenting the outercontour of the preliminary implant model further comprises providing asecond cross-sectional view of the preliminary implant model in acoronal plane, providing on the second cross-sectional view a verticalline tangent to a most lateral portion of a zygomatic arch of the skullof the patient, and providing on the second cross-sectional view acontour line from a temporal crest of the skull until the contour lineintersects the vertical line tangent to the most lateral portion of thezygomatic arch in the second cross-sectional view, the contour linerepresenting a second portion of the augmented outer contour of thepreliminary implant model. The coronal plane of the firstcross-sectional view is more posterior than the coronal plane of thesecond cross-sectional view.

In still yet another embodiment of this first aspect, augmenting theouter contour of the preliminary implant occurs in a plurality ofcross-sectional views in the coronal plane.

In still yet another embodiment of this first aspect, augmenting theouter contour of the preliminary implant occurs in a plurality ofcross-sectional views in an axial plane.

In still yet another embodiment of this first aspect, augmenting theouter contour of the preliminary implant occurs in a plurality ofcross-sectional views in a sagittal plane.

In still yet another embodiment of this first aspect, thepatient-specific craniofacial implant is manufactured from alloplasticand/or absorbable biologic materials selected from one member of a groupconsisting of polymethylmethacrylate (PMMA), polyetheretherketone(PEEK), and porous high-density polyethylene (MedPor). Other biologicmaterials or tissue-engineered substrates may be used in both allograftand xenograft origin using the patient-specific craniofacial implantdesign processes described herein.

A second aspect of the present invention is a craniofacial implantcomprising a base portion having an outer surface curved in a medial tolateral direction, a superior to inferior direction, and a posterior toanterior direction, and a curved augment portion protruding outwardlyfrom the outer surface of the base portion in the medial to lateraldirection to restore proper appearance anywhere along the temporalskeleton when both a hard tissue deformity and soft tissue deformityco-exist. The craniofacial implant of the present invention could alsobe designed for soft-tissue only defects, providing the surgeon a newmethod to camouflage assymetries —both from congential and acquiredetiologies.

In one embodiment of this second aspect, the curved augment portion ofthe craniofacial implant has an outer surface curved in the medial tolateral direction, the superior to inferior direction, and the posteriorto anterior direction.

In another embodiment of this second aspect, the outer surface of thebase portion and the augment portion has a first radius of curvature inthe medial to lateral direction, and wherein the first radius ofcurvature of the base portion is larger than the first radius ofcurvature of the augment portion.

In yet another embodiment of this second aspect, the outer surface ofthe base portion and the augment portion has a second radius ofcurvature in the superior to inferior direction, and wherein the secondradius of curvature of the base portion is larger than the second radiusof curvature of the augment portion.

In yet another embodiment of this second aspect, the outer surface ofthe base portion and the augment portion has a third radius of curvaturein the posterior to anterior direction, and wherein the third radius ofcurvature of the base portion is larger than the third radius ofcurvature of the augment portion.

In yet another embodiment of this second aspect, the outer surfaces ofthe base portion and the augment portion are convex.

In still yet another embodiment of this second aspect, the base portionand the augment portion each have concave inner surfaces.

In still yet another embodiment of this second aspect, the base portionhas a lateral side that forms a perimeter of the craniofacial implant.

In still yet another embodiment of this second aspect, the augmentportion has a lateral side that forms a portion of a perimeter of thebase portion.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the subject matter of the presentinvention and the various advantages thereof can be realized byreference to the following detailed description in which reference ismade to the accompanying drawings in which:

FIG. 1A is a perspective view of a patient's face exhibiting temporalhollowing in the pterional region of the skull.

FIG. 1B is a perspective view of the patient's face of FIG. 1A with arepaired pterional region such that the temporal hollowing has beencorrected.

FIG. 2 is a perspective view of a patient's skull exhibiting a largebone void predominately positioned in the temporal lobe thereof.

FIG. 3A is a frontal view of one embodiment of a patient-specificcranial implant of the present invention designed to fill a bone void ina skull of a patient.

FIG. 3B is a lateral view of an outer surface of the patient-specificcranial implant of FIG. A.

FIG. 3C is a lateral view of an inner surface of the patient-specificcranial implant of FIG. 3A.

FIG. 4A is a 3D reconstruction of a patient-specific cranial implant ofthe present invention having filled a void in the skull of a patient,the patient-specific cranial implant having an augmented portionprojecting outwardly from a base portion.

FIG. 4B is a coronal cross-section of the 3D reconstruction of FIG. 4Ataken along the section line shown in FIG. 4A, the cross-section showingthe relationship between the base portion and the augmented portion ofthe patient-specific cranial implant.

FIG. 5A is a 3D reconstruction of the patient-specific cranial implantof FIG. 4A wherein the augmented portion thereof is shown having an areaapproximately the area of the box with arrows overlying the implant.

FIG. 5B is a coronal cross-section of the 3D reconstruction of FIG. 5Ataken along line 5B thereof showing the location of the most lateralportion of the augmented portion of the patient-specific cranialimplant.

FIG. 6A is a lateral view of the 3D reconstruction of thepatient-specific cranial implant.

FIG. 6B is a frontal view of the 3D reconstruction of thepatient-specific cranial implant shown in FIG. 6A.

FIG. 7A is a lateral view of a 3D reconstruction of another embodimentof a patient-specific cranial implant having a base portion and at leastone augmented portion.

FIG. 7B is a coronal cross-section of the 3D reconstruction of FIG. 7Ataken along line 7B thereof, the cross-section showing the configurationof the base portion and the augmented portion at a posterior location ofthe pterional region of the skull.

FIG. 7C is another lateral view of a 3D reconstruction of thepatient-specific cranial implant of FIG. 7A.

FIG. 7D is a coronal cross-section of the 3D reconstruction of FIG. 7Ctaken along line 7D thereof, the cross-section showing the configurationof the base portion and the augment portion at a central location of thepterional region of the skull.

FIG. 7E is yet another lateral view of a 3D reconstruction of thepatient-specific cranial implant of FIG. 7A.

FIG. 7F is a coronal cross-section of the 3D reconstruction of FIG. 7Etaken along line 7F thereof, the cross-section showing the configurationof the base portion and the augmented portion at an anterior location ofthe pterional region of the skull.

FIG. 8A is a frontal view of a 3D reconstruction of the patient-specificcranial implant shown in FIG. 7A.

FIG. 8B is an axial cross-section of the 3D reconstruction of FIG. 8Ataken along line 8B thereof, the cross-section showing the configurationof the base portion and the augmented portion at a superior location ofthe pterional region of the skull.

FIG. 8C is another frontal view of a 3D reconstruction of thepatient-specific cranial implant of FIG. 7A.

FIG. 8D is an axial cross-section of the 3D reconstruction of FIG. 8Ctaken along line 8D thereof, the cross-section showing the configurationof the base portion and the augmented portion at a central location ofthe pterional region of the skull.

FIG. 8E is yet another frontal view of a 3D reconstruction of thepatient-specific cranial implant of FIG. 7A.

FIG. 8F is an axial cross-section of the 3D reconstruction of FIG. 8Etaken along line 8F thereof, the cross-section showing the configurationof the base portion and the augmented portion at an inferior location ofthe pterional region of the skull.

DETAILED DESCRIPTION

FIG. 1A is a perspective view of a patient's face 100 exhibitingtemporal hollowing 120 in the pterional region of the skull of thepatient. The size, shape and location of such temporal hollowing of apatient may differ based on patient's anatomy as well as the type ofinjury and/or the amount of tissue atrophy incurred by the patient inthis region.

FIG. 1B is a perspective view of the patient's face with a repairedpterional region such that the temporal hollowing has been corrected andis no longer present. After an initial surgery to correct a bony void isperformed, a subsequent procedure using a pterional graft, PMMA, filler,absorbable material or tissue engineered substrate, for example, may beperformed in order to repair the soft tissue defect. The subsequentprocedure may be conducted via injection of PMMA percutaneously intothis region or by placing a pterional flap through a small incision madein the skin. However, a patient will likely exhibit aesthetic asymmetrybetween the time of the initial surgery and the subsequent revisionsurgery to correct the temporal hollowing shown in FIG. 1A. Thepatient-specific cranial implants and methods of designing such implantsof the present invention together provide simultaneous customized hardtissue (i.e. bony) reconstruction and soft tissue (i.e. fat/muscle)reconstruction in a single procedure approach such that temporalhollowing is avoided and revision procedures will not be required.

FIG. 2 is a perspective view of a patient's skull 200 exhibiting a largeirregularly shaped bone void 210 predominately positioned in thetemporal lobe thereof. FIGS. 3A-3C show one embodiment of apatient-specific cranial implant 300 of the present invention designedto fill a bone void, such as shown in FIG. 2, for example.Patient-specific cranial implant 300 includes a perimeter 320 configuredto contact a perimeter 220 of bone void 210 when patient-specificcranial implant 300 is coupled to bone void 210 in a preoperativelyplanned position. Upon coupling of patient-specific cranial implant 300to bone void 210, plates, fasteners and/or adhesive glue, for example,may be used around perimeters 220, 320 of bone void 210 and implant 300,respectively, in order to fix the position of implant 300 with respectto bone void 210. A description of such plates and fasteners used tocouple a patient-specific implant to a perimeter of a bone void is shownand described in the surgical protocol titled “Stryker CMF CustomizedImplant PEEK,” the disclosure of which is incorporated by referenceherein in its entirety.

Implant 300 includes a base portion 340 and an augment portion 360. Baseportion 340 includes a convex outer surface 342 and a concave innersurface 344. Outer and inner surfaces 342, 344 of base portion 340 arepreferably curved in a superior to inferior direction, a posterior toanterior direction, and a medial to lateral direction. Augment portion360 protrudes outwardly from base portion 340 in the medial to lateraldirection. Augment portion 360 includes a convex outer surface 362 thatis also preferably curved in the superior to inferior direction, theposterior to anterior direction, and the medial to lateral direction.

Base portion 340 and augment portion 360 each have a first radius ofcurvature in the superior to inferior direction, a second radius ofcurvature in the posterior to anterior direction and a third radius ofcurvature in the medial to lateral direction. The first, second andthird radii of curvature of the base portion 340 are all larger than thefirst, second and third radii of curvature of the augment portion 360,respectively. Therefore, base portion 340 is flatter and not as steeplyshaped as augment portion 360. The radii of curvature are generally notconstant along any one direction for each of the base portion 340 andaugment portion 360.

Augment portion 360 has a lateral side 370 that preferably forms aportion of a perimeter 350 of base portion 340. The location of augmentportion 360 with respect to base portion 360 is such that lateral side370 of augment portion 360 preferably forms a portion of perimeter 320of implant 300 along with perimeter 350 of base portion 340.

When cranial implant 300 is implanted, the most lateral portion of outersurface 362 of augment portion 360 is preferably located on a linetangent to the most lateral portion of the zygomatic arch, the linebeing substantially parallel to the sagittal plane of the patient.Augment portion 360 also extends as far posteriorly as it doessuperiorly so that an area of augment portion is roughly square.

A method of designing a patient-specific craniofacial implant, such ascranial implant 300, for filling a void in a skull of a patient and forreplacing soft tissue is shown in FIGS. 4A-6B. A tomographic scan suchas a computed tomography (“CT”) scan of a patient with a lateral cranialdefect that fully or partially extends into the pterional region of theskull is first taken. Off the shelf CT segmentation software is thenused to create a three dimensional (“3D”) model of the patient's craniumincluding the lateral cranial defect. A patient-specific craniofacialimplant is then designed using computer aided design (“CAD”) software.The patient-specific 3D implant will fill the bony void left by acraniotomy, for example, and also augment the visible temporal portionsof the patient's head.

Using the CAD software, a preliminary implant model 400 is designed bymirroring contralateral bone of the lateral cranial defect. Generally,the contralateral bone is mirrored off of the central sagittal plane 410as shown in FIG. 4B of a patient's skull in order to define the size,shape and location of preliminary implant model 400 with respect to thecranial defect. Models of deformed or missing segments of internalstructures, such as a lateral cranial defect, may also be constructedfrom coordinate data specifying the deformed or missing segment that isderived from representations of a normal mirror image segment of thestructure. For example, coordinate data defining a mirror image segmentof a structure is useful in the construction of an implantableprosthetic inlay that is to replace a missing segment of a generallysymmetrical internal anatomic structure as shown and described in U.S.Pat. No. 4,436,684 to White entitled, “Method of Forming ImplantableProsthesis for Reconstructive Surgery,” the disclosure of which ishereby incorporated by reference in its entirety. In instances wherebilateral deformities exist, the dual-purpose implants of the presentinvention may be at least partly designed using standard gender-specificdimensions.

While preliminary implant model 400 may be designed using any one ormore of the above described methods, it represents a traditionalcustomized implant that does not account for soft tissue in thepterional/temporal region. In a method of the present invention,preliminary implant model 400 is used as a guide during subsequentdesign steps. The outer contour 420 of preliminary implant model 400 isaugmented in order to account for the soft tissue loss.

Preliminary implant model 400 is designed to have a perimeter thatcontacts the entire perimeter of the bone void. Augment portion 500 isdesigned to augment the pterion in order to counter the effects oftemporal hollowing. Careful attention is made not to include excessmaterial inferiorly which may contribute to mandibular interferenceknown as trismus. The CT coronal cross section of FIG. 4B shows thedifference between preliminary implant model 400 and an updated implantmodel including augment portion 500. In some design processes, augmentportion 500 may only project outwardly from preliminary implant model400 such that it does not span the entire length of a bone void, andtherefore does not contact the entire perimeter of the bone void as doesthe preliminary implant model. As can be seen in FIG. 4B, for example,augment portion 500 is not symmetric to contralateral bone as ispreliminary implant model 400. Together, preliminary implant model 400and augment portion 500 form an updated implant model 600 as shown inFIG. 4A. This figure also includes a directional legend with arrows inthree dimensions. S, I, M, L, P and A on this legend, and any otherlegend in the drawings, stand for superior, inferior, medial, lateral,posterior and anterior, respectively. Most of the bulk reproduction ofthe soft tissue in the pterion region, which is represented by augmentportion 500, occurs at the anterior, lateral, inferior portion of thetemporal skull.

In determining the location of the most lateral portion of the outersurface of augment portion 500, the preliminary implant model 400 isextended laterally away from sagittal plane 410, for example, until theouter surface of augment portion 500 meets the most lateral portion ofthe zygomatic arch 550 of the patient as shown in FIG. 5B. The mostlateral portion of the zygomatic arch is depicted by vertical line 540in the coronal cross section shown in FIG. 5B. In the coronal plane, thetemporal region of the preliminary implant model is augmented by drawinga substantially straight or slightly curved line 560 from the temporalcrest 530 until line 560 intersects vertical line 540 adjacent the mostlateral portion of the zygomatic arch 550. Temporal crest 530 is locatedat the point where there is a change in tangency of the pterional skullas pertinent in the present scenario. Of note, various other areas ofthe temporal (i.e. pterional) skeleton could be assessed fordual-purpose reconstruction. This process is preferably repeated inseveral different two dimensional (“2D”) coronal cross-sections. Theupdated implant models created in the 2D cross-sections are thencombined using the CT segmentation software in order to create the 3Dupdated implant model shown in FIGS. 6A-6B, for example.

As shown in FIGS. 6A-6B, augment portion 500 extends posteriorly fromthe lateral orbital rim 575 to a vertical line 580 perpendicular to thesagittal plane drawn through the external acoustic meatus 585. Augmentportion 500 should extend as far posteriorly as it does superiorly sothat the augmented area is roughly square as shown in FIG. 5A. Theaugmented area is roughly outlined by box 570 overlying updated implantmodel 600 in FIG. 5A.

FIGS. 7A, 7C, and 7E are a series of lateral views of a 3Dreconstruction of one embodiment of an updated implant model 600implanted in a model of a bone void of a patient's skull 610, each ofthese views including a section line 7B, 7D, and 7F, respectively.Section lines 7B, 7D, and 7F are each situated at different locations onthe 3D models. Section line 7B is located in a posterior region, sectionline 7D is located in a central region, and section line 7F is locatedin an anterior aspect of the pterional region of the patient's skull 610in these lateral views. FIGS. 7B, 7D and 7F are coronal cross-sectionalviews that correspond to FIGS. 7A, 7C and 7E, respectively. Each ofthese coronal cross-sectional views show updated implant model 600including a preliminary implant model 700 and an augment portion 800. Ascan be seen most clearly in FIG. 7D, augment portion 800 is notsymmetric to contralateral bone as is preliminary implant model 700.Most of the bulk reproduction of augment portion 800 is created in thiscentral region of the pterion.

FIGS. 8A, 8C, and 8E are a series of frontal views of updated implantmodel 600 each having a section line 8B, 8D, and 8F, respectively.Section lines 8B, 8D, and 8F are each situated at different locations onthe 3D models. Section line 8B is located in a superior region, sectionline 7D is located in a central region, and section line 8F is locatedin an inferior aspect of the pterional region of the patient's skull inthese lateral views. FIGS. 8B, 8D and 8F are axial cross-sectional viewsthat correspond to FIGS. 8A, 8C and 8E, respectively. Each of theseaxial cross-sectional views shows the difference between preliminaryimplant model 700 and an updated implant model including augment portion800. As can be seen most clearly in FIG. 8D, augment portion 800 is notsymmetric to contralateral bone as is preliminary implant model 700. Itis designed and modified specifically to make up for the soft tissuediscrepancy. In other words, it can be used for deformity prophylaxisand/or secondary correction.

Each patient-specific cranial implant of the present invention will becustomized to fit the unique bony void and individual anthropometry ofthe patient, and therefore, the design inputs described above may beadjusted as needed. For example, with respect to bilateral deficits, thedual-purpose implants can be fabricated used gender-specificanthropometric norms. Once the design of updated implant model 600 isfinalized using the CAD software, a patient-specific craniofacialimplant may be manufactured using any one of many known manufacturingtechniques, such as steriolithography, milling, and molding, forexample. The implant can then be manufactured, for example, fromalloplastic materials such as PMMA, MEDPOR®, and PEEK.

Although the invention herein has been described with reference toparticular embodiments, it is to be understood that these embodimentsare merely illustrative of the principles and applications of thepresent invention. It is, therefore, to be understood that numerousmodifications may be made to the illustrative embodiments and that otherarrangements may be devised without departing from the spirit and scopeof the present invention as defined by the appended claims.

1. A method of designing a craniofacial implant for filling a void in askull of a patient and for replacing soft tissue comprising: creating athree dimensional model of the skull having the void; creating apreliminary implant model configured to replace the void in the skull;and creating an updated implant model by augmenting an outer contour ofthe preliminary implant model to account for soft tissue loss overlyingat least a portion of the void.
 2. The method of claim 1, furtherincluding taking tomographic images of the skull of the patient in orderto create the three dimensional model of the skull including the void.3. The method of claim 1, wherein the preliminary model is created bymirroring contralateral bone of the void.
 4. The method of claim 3,wherein mirroring contralateral bone of the void occurs about a sagittalplane of the patient.
 5. The method of claim 1, wherein augmenting theouter contour of the preliminary implant model comprises: providing afirst cross-sectional view of the preliminary implant model; providingon the first cross-sectional view a vertical line tangent to a mostlateral portion of a zygomatic arch of the skull of the patient; andproviding on the first cross-sectional view a contour line from atemporal crest of the skull until the contour line intersects thevertical line, the contour line representing a first portion of theaugmented outer contour of the preliminary implant model.
 6. The methodof claim 5, wherein augmenting the outer contour of the preliminaryimplant model further comprises: providing a second cross-sectional viewof the preliminary implant model; providing on the secondcross-sectional view a vertical line tangent to a most lateral portionof a zygomatic arch of the skull of the patient; and providing on thesecond cross-sectional view a contour line from a temporal crest of theskull until the contour line intersects the vertical line, the contourline representing a second portion of the augmented outer contour of thepreliminary implant model.
 7. The method of claim 6, wherein the firstand second cross-sectional views of the preliminary implant model areprovided in a coronal plane.
 8. The method of claim 7, wherein thecoronal plane of the first cross-sectional view is more posterior withrespect to the skull of the patient than is the coronal plane of thesecond cross-sectional view.
 9. The method of claim 6, wherein the firstand second cross-sectional views of the preliminary implant model areprovided in a axial plane, and wherein the axial plane of the firstcross-sectional view is more superior with respect to the skull of thepatient than is the axial plane of the second cross-sectional view. 10.The method of claim 6, wherein the first and second cross-sectionalviews of the preliminary implant model are provided in a sagittal plane,and wherein the sagittal plane of the first cross-sectional view is moremedial with respect to the skull of the patient than is the sagittalplane of the second cross-sectional view.
 11. The method of claim 1,wherein the patient-specific craniofacial implant is manufactured fromalloplastic materials selected from one member of a group consisting ofpolymethylmethacrylate, polyetheretherketone, and porous high-densitypolyethylene.
 12. A craniofacial implant comprising: a base portionhaving an outer surface curved in a medial to lateral direction, asuperior to inferior direction, and a posterior to anterior direction;and a curved augment portion protruding outwardly from the outer surfaceof the base portion in the medial to lateral direction.
 13. Thecraniofacial implant of claim 12, wherein the curved augment portion hasan outer surface curved in the medial to lateral direction, the superiorto inferior direction, and the posterior to anterior direction.
 14. Thecraniofacial implant of claim 13, wherein the outer surface of the baseportion and the augment portion has a first radius of curvature in themedial to lateral direction, and wherein the first radius of curvatureof the base portion is larger than the first radius of curvature of theaugment portion.
 15. The craniofacial implant of claim 14, wherein theouter surface of the base portion and the augment portion has a secondradius of curvature in the superior to inferior direction, and whereinthe second radius of curvature of the base portion is larger than thesecond radius of curvature of the augment portion.
 16. The craniofacialimplant of claim 15, wherein the outer surface of the base portion andthe augment portion has a third radius of curvature in the posterior toanterior direction, and wherein the third radius of curvature of thebase portion is larger than the third radius of curvature of the augmentportion.
 17. The craniofacial implant of claim 13, wherein the outersurfaces of the base portion and the augment portion are convex.
 18. Thecraniofacial implant of claim 17, wherein the base portion and theaugment portion each have concave inner surfaces.
 19. The craniofacialimplant of claim 12, wherein the base portion has a lateral side thatforms a perimeter of the craniofacial implant.
 20. The craniofacialimplant of claim 19, wherein the augment portion has a lateral side thatforms a portion of a perimeter of the base portion.
 21. A method ofmanufacturing a craniofacial implant for filling a void in a skull of apatient and for replacing soft tissue comprising: creating a threedimensional model of the skull having the void; creating a preliminaryimplant model configured to replace the void in the skull; creating anupdated implant model by augmenting an outer contour of the preliminaryimplant model to account for soft tissue loss overlying at least aportion of the void; and fabricating the updated implant model.